Is it fine to store my boards in my trunk all summer? I live in AR so it gets pretty damn toasty. Will it warp the decks or fuck with the bushings/wheels?
All good answers so far, but here is a story from my experience too.
I had one guy I know from the local skatepark who had a sporty hatch looking vehicle, never covered his boards in the back, always complained that his boards kept getting stress cracks down the length and quite a few even had delamination issues, even though he never skated that hard or broke a board skating. Others had told him not to leave his boards in the car like that, but he didn't want to listen and I refused to sell him any more decks with him coming back to complain about the wood.
Another half a dozen assorted brands from other shops all had the same issue. Then when he crashed his fancy car and got a van, his next new board magically had no issues, along with others from then on. It still took a lot of convincing for him to understand direct light and significant heat would always cause the board to cook in his car, but quite simply putting it in a cardboard board box or even just putting something insulating it from the heat over the board would help a whole lot in stopping those issues.
As for any other things, they all are minimal in comparison to that issue, but I always recommend anyone who is going to leave anything in their car to put it in a closed box, which is pretty good insulation and helps keep boards, decks and any other product safe, as well as out of sight of possible theft from someone seeing a skateboard in a locked car and smashing a window - yes that has happened to others more than a few times over the years too.
If you don't have any board boxes, next time you order something, or even drop in to the local shop and buy something, just ask them for a board box as most places will have quite a few headed for the bin that can be reused for a safe car board storage box.
I have almost permanently kept boards in my car for the last twenty something years, including having the car out in full sun day in, day out for a lot of that and I never really had any issues with any of my boards, spare decks or anything else. Everything is in cardboard boxes in both the boot and interior, with a thick dark material over the lot on the back seat which has definitely helped.